1. Field of the Invention
The present invention relates to a room-temperature curable organopolysiloxane composition used as a sealing material, or as an adhesive for electrical components or electronic components, which produces a silicone rubber with excellent adhesion to a variety of synthetic resin substrates (that is, adherends).
2. Description of the Prior Art
Room-temperature curable silicone rubbers which undergo cross linking in the presence of moisture are easy to handle, and offer excellent weather resistance and electrical characteristics, and are consequently used in a variety of fields including as sealing materials for construction, and adhesives for bonding or securing electrical components or electronic components. In recent years, as the technology relating to the durability of synthetic resins has improved, the number of cases in which conventionally available room-temperature curable silicone rubbers will not bond well to substrates formed from these synthetic resins has increased.
Examples of methods of improving the adhesion of room-temperature curable silicone rubbers involve the incorporation of an adhesion improving agent such as an alkoxysilane with an aminoalkyl group such as 3-aminopropyltriethoxysilane or a silane compound with an oxime group and an alkoxy group (Japanese Post-Examination Patent publication (kokoku) No. 46-11272 (JP46-11272B), Japanese Post-Examination Patent publication (kokoku) No. 56-9560 (JP56-950B)). By incorporating this type of agent, the initial adhesion is improved, although on long term storage of the composition, the adhesion deteriorates.
Furthermore, methods of improving the adhesion by incorporating a specific filler have also been proposed (Japanese Patent publication No. 3146192 (JP3146192B), Japanese Laid-open publication (kokai) No. 10-168320 (JP10-168320A), Japanese Laid-open publication (kokai) No. 10-316811 (JP10-316811A)). Because these fillers comprise mainly water absorbent calcium carbonate, the moisture content must be removed from the calcium carbonate either prior to, or during the addition of the filler to the room-temperature curable silicone rubber, which undergoes cross linking in the presence of moisture, and the increased complexity of the process is not particularly desirable.
A room-temperature curable composition in which 0.001 to 10 parts by weight of an iron oxide ferrite is added per 100 parts by weight of a base polymer to improve heat resistance of the cured rubber has also been proposed (Japanese Laid-open publication (kokai) No. 52-45655 (JP52-45655A)). However, the quantity of the ferrite is so small that the ferrite is not effective very much in improvement of adhesion to the synthetic resin substrates.